> I get the feeling that those in law enforcement are so brainwashed as to the monstrous nature of their "enemy" that they rationalise away "collateral damage" like this guy as a necessary evil.

I'm sure that on some level they feel bad about it, but they find ways to rationalize it away so they they can continue their job, and the politicos in the department try to keep everyone hush-hush to avoid lawsuits and a PR storm if someone were to admit to a mistake.